This application is based on Japanese Patent Applications No. 2003-75018 filed on Mar. 19, 2003, the disclosures of which are incorporated herein by reference.
The present invention relates to a pressure sensor device for detecting pressure of a measuring object, and more particularly to a pressure sensor device having a pressure sensor and a temperature sensor for detecting both pressure and temperature of the measuring object. The present invention further relates to a method of fixing the temperature sensor in the pressure sensor device.
A pressure sensor device having a temperature sensor, i.e., the pressure sensor device integrated with the temperature sensor, is, for example, used for an internal combustion engine of an automotive vehicle. The device detects both pressure and temperature of intake air as a measuring object in an intake manifold of the engine, so that the device outputs a measurement signal to a controller. The controller calculates and outputs a control signal to an engine of the vehicle so that the engine is controlled.
A conventional pressure sensor device will be explained with reference to FIG. 6. The pressure sensor device (1) includes a sensor casing (3), a connector pin (11), a pressure sensor (which comprises a pressure sensor chip 5, a mold IC 2 and so on), and a temperature sensor (21). The connector pin (11) is connected to an outside circuit such as an electronic control unit (i.e., ECU) as a controller of the vehicle. Each of the pressure sensor (2 and 5) and the temperature sensor (21) are electrically connected to the connector pin (11), respectively. Particularly, the temperature sensor (21) is connected to the connector pin (11) at a connection portion (20) through a pair of lead wires (19). The lead wire (19) is protruded from the connection portion (20). The temperature sensor (21) is disposed on one end of the lead wire (19), and the connection portion (20) is disposed on the other end of the lead wire (19). Thus, the temperature sensor (21) is accommodated in a temperature sensor chamber (16b) so that the temperature sensor (21) is supported by the connection portion (20) through the lead wire (19). In other words, the temperature sensor (21) is floated in the temperature sensor chamber (16b) with using the lead wire (19) as a support.
An inlet port (13) is adhered to the sensor casing (3) and a partition plate (40) is formed in a lower portion (a pressure introduction port 16) of the inlet port (13) so as to divide into two parts, one of which is a pressure introduction passage (16a) and the other is the temperature sensor chamber (16b).
As mentioned above, since the connection portion (20) is only the support of the temperature sensor (21), the temperature sensor (21) is vibrated sympathetically with the connection portion as a supporting point in a case where a vibration is applied to the sensor device (1). Accordingly, a stress is applied to the connection portion (20) repeatedly, so that the lead wire (19) may be broken at the connection portion (20). Moreover, the lead wire (19) or the temperature sensor (21) may hit an inner wall of the temperature sensor chamber (16b), so that the lead wire (19) or the temperature sensor (21) is broken.
In order to solve the above mentioned problem, inventors of the same applicant of this invention have proposed a new temperature and pressure sensor device, which is disclosed in Japanese Patent Application of No. 2002-308982 filed on Oct. 23, 2002. Such a new sensor device will be explained for reference with reference to FIG. 7. In this device shown in FIG. 7, a vibration reduction means (41), such as a buffer made of synthetic resin, is provided between a lead wire (19) and an inner wall of a pressure introduction port (16), in order to suppress the vibration applied to a temperature sensor (21). It is, however, disadvantageous in that a lower end of the pressure introduction port of the inlet port shall be divided into two parts, one for passing through a measuring object to a pressure sensor and the other for holding the temperature sensor. As a result, such lower end of the inlet port will be larger and it will become harder to mount a sensor device onto an internal combustion engine.
It is, therefore, an object of the present invention to provide a smaller pressure sensor device having a temperature sensor, in which the temperature sensor is rigidly held to suppress a vibration thereof, and to provide a method of fixing and holding the temperature sensor in the pressure sensor device.
According to a feature of this invention, a pressure sensor device comprises a pressure sensor for detecting pressure of a measuring object, a temperature sensor for detecting temperature of the measuring object, a sensor casing for accommodating the pressure sensor and a connector pin, which are electrically connected to the pressure sensor and an outside circuit, an inlet port mounted on the sensor casing and having a pressure introduction port for introducing the measuring object to the pressure sensor disposed in the sensor casing, wherein the temperature sensor is disposed in the pressure introduction port. The temperature sensor comprises a pair of lead wires and a temperature sensing element, wherein the pair of lead wires is connected at its one end to the connector pin and to the temperature sensing element at the other end, so as to electrically connect the sensing element with the outside circuit as well as to mechanically support and hold the sensing element in the pressure introduction port. The pair of lead wires is made of elastic metal and supports the sensing element with an elastically deformed condition so that a reaction force of the lead wires is applied to the lead wires and the sensing element to urge and press the sensing element to an inner wall of the pressure introduction port.
As a result, the temperature sensor of the lead wires and sensing element are rigidly fixed to the pressure sensor device at a contact point between the sensing element and the inner wall and at another contact point between the lead wire and the inner wall of the port, other than at the connection portion at which the one ends of the lead wires are welded to the connector pin. In this sensor device, accordingly, the vibration to be applied to the temperature sensor can be suppressed and its durability is improved.
Since the temperature sensor is disposed in the pressure introduction port and rigidly held at its position by use of the reaction force of the lead wires, it is possible to pass the measuring object to the pressure sensor through the pressure introduction port. It is, therefore, not necessary to divide the pressure introduction port into two parts, one for passing the measuring object to the pressure sensor and the other for holding the temperature sensor. Accordingly, an outer diameter of the pressure introduction port can be made smaller and it becomes easier to mount the sensor device of a smaller size onto an internal combustion engine.
In the embodiment of the present invention, one end of the lead wire is formed as a U-shape and this U-shaped portion of the lead wire is elastically deformed when the temperature sensor is inserted into the pressure introduction port, so that an reaction force generated by this deformed U-shaped portion is applied to the lead wire and the temperature sensing element to outwardly urge them towards the inner wall of the port. As a result, vibration of the temperature sensor is suppressed.
Another feature of this invention relates to a fixing method of the temperature sensor to the pressure sensor device of the above mentioned construction. The feature of this fixing method comprises a step of forming one end of the lead wire as a U-shape, so that a distance between the sensing element and the opposing lead wire becomes larger than an inner diameter of the pressure introduction port while a distance of the opposing portions of the U-shaped lead wire is made smaller than the inner diameter; a step of connecting ends of the pair of the lead wires to the connector pin; a step of inserting the temperature sensor (the temperature sensing element and the lead wires) into the pressure introduction port of the inlet port; and a step of adhering the inlet port to the sensor casing, wherein at the step of inserting the temperature sensor into the pressure introduction port, a part of the lead wires is elastically deformed so as to generate a reaction force at the lead wires and to urge, by the use of this reaction force, the temperature sensing element to the inner wall of the pressure introduction port, thereby to rigidly hold the temperature sensor in the sensor device.